Infection following bony fracture is one of the most prevalent and challenging complications in trauma patients with an estimated annual cost of $35 billion in the US. (https://stacks.cdc.gov/view/cdc/11550) Recurrent infection rates are unacceptably high at 30%, resulting in prolonged morbidity, loss of function, and/or loss of limb. Vascular perfusion plays a critical role in the health of bone by delivering necessary oxygen, nutrients, antibiotics, and endogenous immune cells. The management of bony infection is therefore based on aggressive, thorough debridement in an effort to remove all poorly perfused bone through visual and tactile clues such as color, turgor and extent of soft tissue stripping. However, there are no objectively measurable or quantifiable methods to assess the bone perfusion and the success of removing devitalized bone is based almost entirely on surgeon?s experience. Thus, the overall goal of this proposal is to develop and evaluate an indocyanine green (ICG)-based dynamic contrast-enhanced fluorescence imaging (DCE-FI) to objectively assess bone perfusion and guide surgical debridement. The scientific premise of this proposal is underpinned by data from our prior pre-clinical work in a porcine model and our pilot clinical study applying ICG-based DCE-FI to assess bone perfusion in patients during orthopaedic surgery. In these studies, we established that DCE-FI can quantitatively assess bone perfusion in a measurable, reproducible and predictable manner, and we developed analytic models differentiating the endosteal from periosteal contribution to total blood supply. This model was then able to effectively differentiate healthy from damaged bone with a linear decision boundary with 89% accuracy, in the pre-clinical porcine study. To attain our overall objective, three aims will be pursued. In Aim 1 we will assess the relationship between post-debridement bone perfusion, as measured using ICG-based DCE-FI, and recurrent infection/treatment failure. Additionally, we will refine analytic models that assess the relative contribution of endosteal versus periosteal blood supplies. In Aim 2 we will explore the relationship between dynamic contrast-enhanced MRI (DCE-MRI) and DCE-FI to improve the three-dimensional analytic potential of DCE-FI. In Aim 3 we will develop streamlined analytic tools into a user-centered interface that will optimize use of ICG-based DCE-FI derived data in normal surgical workflow. Application of ICG-based DCE-FI has enormous potential to revolutionize treatment of post-traumatic infections by minimizing treatment failure and minimizing bone resection and ultimately revolutionize the standard of care for millions of trauma patients. This project leverages an extensive infrastructure and experience in fluorescence-guided surgery as well as longstanding collaborations between surgical subspecialties and biomedical engineers at Dartmouth and R Adams Cowley Shock Trauma Center.